View Full Version : battery damage using mower if not recharging properly?

Ken Platt
06-30-2015, 6:39 PM
Folks -

My riding mower does not seem to be recharging the battery properly, or perhaps not at all. I am waiting for the shipment of replacement parts (alternator, wires, etc), but in the meanwhile the grass is getting pretty high (great rainfall up here the past few weeks).

I torched one battery to discover the problem, and I am trying not to do that to another. If I charge up the battery after a mowing session, am I harming the battery by using the mower?

I was able to mow with the previously-mentioned torched dead battery (it had become unchargable) by jump-starting from my pickup's battery.So, I'm wondering if, after the initial startup of the mower and blade, there's much drain on the battery. (I was kind of desperate to get some mowing done last week during the 1 dry day. The mower started up fine with jumper cable running from the pickup battery, ran fine, and I could start the blade once - it's some sort of solenoid-triggered thing.)

Could I get some advice from those with a bit more knowledge of how these engines and batteries interact? Many thanks -


Dan Hintz
07-01-2015, 6:09 AM
If your alternator is shot, you're using the battery itself to provide power for spark. You may get an hour of mowing out of it, but by that time the battery will be drained... and draining lead cell batteries kills them pretty quickly. Fix your charging system ASAP.

Jerome Stanek
07-01-2015, 7:37 AM
on one of my mowers the ground wire wasn't making a good connection just enough to keep the mower running

Mike Lassiter
07-01-2015, 7:45 AM
most small engines don't need battery power to run as they use magnet(s) in the flywheel and magnetos creating the spark for the sparkplug. Howhere there is an electric clutch that engages the blade(s) that will draw power. This is how most mowers made for some time disengage the blades when you are mowing and start moving in reverse. It is a safety feature that is easily controled with a switch since the blades are being engaged by a electric clutch.

I have a BCS walk behind tractor that I just installed a new battery on. The battery is about $75, and comparable to riding mower size. I was surprised that it was so much. I would minimize running time to 30 - 45 minutes and use a small low amp charger in between to slowly recharge it to avoid overheating it.

I think the bigger issue would be the electric clutch. As the battery becomes discharged the voltage will drop. You could overload the clutch if you are cutting fairly tall grass and cause it to start slipping. That will kill it in very short order. Replacing a electric clutch is an expensive propersition. Several hundred dollars for the part alone if you diy.

Mike Wilkins
07-01-2015, 9:31 AM
My riding mower battery has been comatose for most of the year. I just use one of those portable jump boxes to give it a jump and off I go. I really do need to get a battery soon though.

Ole Anderson
07-01-2015, 10:04 AM
Cheap lawnmower batteries are good for one year. At my NAPA dealer the cheap one was about $40, the better one that lasts 3 years was about $50. Well worth it. Same battery at a JD dealer was almost twice that.

To answer your question, you should not harm the battery by charging it after one mowing session.

Ken Platt
07-01-2015, 9:11 PM
Thanks folks. Seems like the safest course is to hold off mowing until the parts get here, should be in 5 -6 days, hopefully the repair will go smoothly.

Ole, I'm surprised at that time estimate. I've usually had batteries for many years at a time. I do usually get one of the higher CCA batteries, but no particular brand name.

Mike L, I kinda wish I'd kept the old dead battery a while still so I could keep mowing. I wasn't able to start it with my HF charger/starter gizmo, though. I'd just get a hum when I tried.

Mike W, thanks for the explanation. I guess I'm still not clear on what runs off the battery when the mower AND the blades are running. I know that starting the blades needs battery power; I had been finding that when the battery needed charging, the first thing to not work was the blade startup. Weirdly, as I mentioned, with the dead battery I could jump start the motor, then take off the cables, and could start the blades ONCE.I'm not sure I understand that.

I ordered all the parts for the alternator system, wires, stator, rectifier, the works. I figure it's not worth trying to figure out which component is bad. Costs a few more $$ (parts total like $150) but hopefully I'll be up and running soon. Before my yard becomes a complete jungle.